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DefinitionDouble helix, as related to genomics, is a term used to describe the physical structure of DNA. A DNA molecule is made up of two linked strands that wind around each other to resemble a twisted ladder in a helix-like shape. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G) or thymine (T). The two strands are connected by chemical bonds between the bases: adenine bonds with thymine, and cytosine bonds with guanine.
 NarrationThe discovery of DNA's double-helical structure in the 1950s was perhaps the most significant biological accomplishment of the 20th century. Knowledge of this remarkably clever structure, involving two complementary strands of DNA that each provide the template for making the other strand, provided a key insight about how it was that DNA could serve as the information molecule of all living systems. This structural detail about DNA rapidly accelerated research that revealed important aspects about DNA function encodes information for creating and operating living systems. Meanwhile, DNA's double helix has arguably become the most well-known and iconic image associated with biology, perhaps with all of science. SearchNucleic acids form the building blocks of all living organisms. They are a group of complex compounds of linear chains of monomeric nucleotides where each of these nucleotides is made up of a phosphate backbone, sugar, and nitrogenous base. They are involved in the maintenance, replication, and expression of hereditary information. Two of the famous ones are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). The DNA is awe-worthy, holding the key to heredity. RNA is just as impressive, as it pretty much runs the show, with DNA as the main star. Together these molecules ensure that the DNA is replicated, the code is translated, expressed and that things go where they should go. DNA and RNA are very similar to each other while they also manage to be different in just the right way. Introducing DNA and RNAAre you sufficiently freaked out about genetics; and by extension, this power couple (DNA and RNA), what they are, what they do and the implications of their activity? Most people get overwhelmed with genetics. So fear not, here we are going to provide a simple introduction to the similarities between DNA and RNA and their differences, and then try to tie these to their functions and partnership. This way, you will understand the basics before you attempt to delve into the complicated and detailed roles of each. Because of their intertwined fates in the form of the central dogma (Figure 1), we will discuss both the differences and similarities simultaneously. The Central DogmaThe central dogma explains the flow of the genetic code from DNA through all three types RNA to making protein. As you can tell from this, DNA and RNA both contain a chemical code central to the formation of proteins. Without the one, the flow of this information would break down, and that would be the end of life as we know it. The DNA and RNA StructuresStructurally these molecules are very similar with a few differences (Figure 2). They are both made up of monomers called nucleotides. Nucleotides simply refer to nitrogenous bases, pentose sugar together with the phosphate backbone. Both DNA and RNA have four nitrogenous bases each—three of which they share (Cytosine, Adenine, and Guanine) and one that differs between the two (RNA has Uracil while DNA has Thymine). The pairing of these bases is the same between these nucleic acids; namely guanine bonds with cytosine while adenine bonds with thymine, or with uracil in the case of RNA. Secondly, DNA is double-stranded while RNA is single stranded. Thirdly, DNA is more structurally stable compared to RNA. The comparably slight instability allows RNA to be flexible and more accessible and can thus fold into meaningful structures, a property that can be fully appreciated in the proteins RNA makes. Lastly, they both contain a pentose sugar; DNA is a deoxyribose, a characteristic referring to the hydrogen where the hydroxyl group is on the ribose of the RNA molecule (figure 3). One of the most significant similarities between DNA and RNA is that they both have a phosphate backbone to which the bases attach. Because of the phosphate group, this backbone is negatively charged—a quality many genetic techniques appreciate and exploit. Birth, Death, and Maintenance of RNA and DNARNA is continuously made and degraded throughout the life of cells while DNA integrity is crucial. So, instead, DNA continually undergoes DNA replication to ensure this integrity across cells. The body works in various ways to ensure the safety of this structure by continuously keeping all the DNA cleaving enzymes in check. RNA intrinsic function depends on its accessibility, flexibility, and dispensability. Thus, all the “weaknesses” present in this structure are what make it so important and vital to the success of DNA duties. DNA and RNA Dependency, Regeneration and ReplicationDue to the fragile nature of DNA, it resides within the nucleus where it is protected. DNA and RNA form the perfect partners in crime whose primary functions are to ensure gene expression and protein synthesis. RNA is found both in the nucleus and the cytoplasm, this way it can shuttle the DNA message from the nucleus to the targets. RNA is not as fragile and as such can afford to mile around in ways DNA can’t. Because RNA has to move around so much and performs many functions in the synthesis of proteins, different types of RNA are synthesized, and there is a division of labor between them. The three different types of RNA associated with the central dogma are messenger RNA (mRNA), transporter RNA (tRNA) and ribosomal RNA (rRNA). DNA is self-sufficient, providing a template for its DNA replication and the information for RNA synthesis. The antiparallel nature of DNA makes it such that each strand (antiparallel and parallel) can serve as a template and with the aid of numerous proteins can self-duplicate. This is especially integral because when you make new cells they all need to be copies of each other. Location, Location, LocationDNA is a fragile molecule that forms the basis of most, if not all, biological function. As stated before, because of its fragile nature it resides within the nucleus where it is protected. Some DNA is also found in organelles such as mitochondria and chloroplast—think ENDOSYMBIOTIC THEORY to make sense of this (a story for another day). Since DNA needs to maintain its integrity, it is of utmost important to ensure that it is exposed to minimal danger and to ensure this it is confined to the nucleus where several proteins are entrusted with its safety while RNA ensures that the functions of DNA are fulfilled. Uracil and Thymine, Which One is Better?Uracil and Thymine serve a similar in form and function with one important difference—the methyl group (Figure 5 and Figure 6). Thymine is energetically taxing to make while Uracil can be easily assembled through deamination of cytosine. Uracil is more flighty and friendly, occasionally pairing with any other base, including itself. Thus for the integrity of DNA, uracil becomes an unwise choice—hence thymine. So why is it OK for RNA to use uracil, you ask? Well, due to its disposable nature, RNA is not meant to be made for longevity; therefore, cheaper material during its assemblage can be used. To Be Double-Stranded or Single-Stranded is the QuestionWhy is DNA double-stranded? And if this is a good idea why doesn’t RNA do it too? Once again, the integrity of DNA is so important that pretty much everything about it is about keeping it safe. The order and assemblage of the nitrogenous bases are what the genetic code is about, everything around it is—once again—about keeping it safe. Therefore, as you can guess, it would not be wise to leave this precious code exposed. One way of making sure it is concealed then is by having complementary ones strategically facing each other, the adjacent ones held together by the backbone and then proceeding to pack tightly into chromosomes. This way all the harsh dangers in the nucleus are not able to access and thus mutate the genetic code. The presence of two strands also provides the proof against which the other strand can be checked and fixed. So why isn’t RNA doing the same thing? Well, once again RNA doesn’t hang around long enough to warranty such safety precautions, it would be a waste of energy and space—and as we all know, energy (ATP) is a precious commodity in the molecular function of the cell (another story for another day). In addition to this, RNA serves as a template against which the code for protein can be carried, therefore, exposed bases are readily available for this function. What are the Differences Between Deoxyribose and Oxyribose Sugar?The absence of the one Oxygen reduces the reactivity of DNA, ensuring that it does not get involved where it should not, thereby reducing the risk of being broken down. However, given that the majority, if not all, of RNA functions, depend on it being busy and hyper-reactive, it is just as well then that it keeps that Oxygen to ensure maximum functionality. You can think of messenger RNA as an ON, and OFF switch of gene expression and the presence/absence of this Oxygen is central to this function. Recap and ConclusionHopefully this information did not make your head spin. If it did, below you will find a short recap. Both molecules contain a phosphate backbone and are made up of nucleotides. DNA carries all the information needed for DNA replication and transfer new information to new cells. This information is also needed to make proteins the body needs for various purposes including regulation of DNA replication. RNA is transcribed from the DNA to make these proteins (the central dogma, Figure 1). RNA is transcribed and processed within the nucleus, it then moves through the nuclear pores for protein translation in the cytoplasm. In this sense, DNA and RNA are the perfect partners in crime. What DNA can’t do, RNA can and what DNA can do RNA can’t. What results from this perfect partnership is that the single-stranded RNA can be made from the double stranded DNA. The nucleus confined DNA can send its message to the rest of the cell with the aid of the RNA, which moves around freely through the cell. The “dangers” faced by the RNA means it might or does need to be recreated and continuously destroyed, DNA provides the platform for the rebirth of this molecule. By all accounts, DNA and RNA differ in just the right amount while they are also similar just right and hopefully this point was made plenty clear here. Let’s put everything into practice. Try this Biology practice question:Looking for more Biology practice?Check out our other articles on Biology. You can also find thousands of practice questions on Albert.io. Albert.io lets you customize your learning experience to target practice where you need the most help. We’ll give you challenging practice questions to help you achieve mastery in Biology. Start practicing here. Are you a teacher or administrator interested in boosting Biology student outcomes? Learn more about our school licenses here. Which of the following best describes structural difference between DNA and RNA?Which of the following BEST explains a structural difference between DNA and RNA? DNA is usually double-stranded, with both strands parallel in directionality, whereas RNA is usually single-stranded.
What are the structural differences between DNA and RNA quizlet?The three main differences between RNA and DNA is that (1) The sugar in RNA is ribose instead of deoxyribose, (2) RNA is generally single-stranded and not double-stranded , and (3) RNA contain uracil in place of thymine.
Which of the following statements best summarizes the differences between DNA and RNA quizlet?Which of the following statements BEST summarizes structural differences between DNA and RNA? RNA is a protein, while DNA is a nucleic acid.
Which statement correctly describes a difference between DNA and RNA?Which of the following correctly describes a difference between DNA and RNA? DNA occurs in the nucleus, whereas RNA only occurs outside the nucleus.
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Which of the following best describes a structural difference between DNA and RNA quizlet?
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